Dimpling mandrel



DGC- 7, 1948 H. R. FISCHER DIMPLINGl MANDREL A Filed 4.April 4, 1944 yTLV ff m lik xNvENToR Aww/P0 /a//' Efo/[42 Q4 ATTORNEY Nw wfg s Q ATHFIPatented Dec. 7, 1948 UNITED rSTATES PATENT vOFFICE l v 4` Il l'2455Q9o3 ,i

t {DIMPLING MANDREL Howard R. Fischen` Detroit, Mich., assigner AtoChicago Pneumatic v Tool .-Company, yNew York,

N. Y., a corporationof New Jersey Application April4, 1944, Serial No.529,479

y 1 l :A This invention relates to the dimpling'of metal sheets aroundvrivet holes therein in order to adapt the latter for receiving aoountersunk vorA flush type rivet by utilizing a draw pin or mandrelwhen connected to a powered dimpling tool for drawing a pair of dimplingdies together upon said sheets to dimple them. The invention refersparticularly to a rotatable mandrel to be used withmeans for speedilyinserting the mandrel vinto one of the two dimpling dies preparatory todimpling the metal sheets by said dimpling tooland'also;4 for quicklyremoving said mandrehfollowing the dimpling operation and lreinsertingthe mandrel in the die through another rivet hole.

Flush rivets are used extensively in aircraft construction on theexposed surfaces of thefmetal skin which forms a cover for thefuselagefwing sections and other structural `elements` `The metalsheets, usually made-,of aluminum alloy,v are mounted in place and theoverlappingportions thereof are provided with registering perforationsformed by drilling or punching.- `The sheets are dimpled around-theholes to provide recesses for receiving the heads of the rivets. Theresulting structure has the advantages. lof in. creased strength of therivet joint and decreased wind resistance. v Y,

According to one method of dimpling, which is considered to be the mosteffective for certain typesof Work, a draw pin is rinserted from oneside 4of the sheets through the rivet hole and the projecting end on theother side is grasped with a power tool which applies pressure toopposeddimpling dies through the application, of. tensile force to the drawpin, "Assoon a'slthe dimple is formed, the draw" pin or mandrel'r iswithdrawn and moved to the next hole.` The cycle voi" operation mustnecessarily be repeated in krapid succession because of the thousands ofholes required to be dimpled in a single airplane. j l y Thus it is amain 'object of thisfinventionto provide facilities `for speeding up.vthe dimpling cycle as alwhole by facilitating'l speedyj initialinsertion of the mandrel into the one 'dimpling die and alsoy finalWithdrawal ofsaid' mandrel from the latter in such leiiicient manner'vas to save time during each cycle'of the operation.` l It is also anobject to minimize any loss of vtime resulting from occasional breakageof the mandrel and to allow rapid removal of the broken mandrel partsfrom the die and replacement byvfa new mandrel. n A special feature ofthe invention is the use f l a screw type mandrel with acorrespending'screw type dimpling die and a handle'to allowinsertion y'of the mandrel with simultaneous placing'ofthe@ 6 claims.' (el. 153-41)die preparatory to subsequent dimpling of metal sheets in very closequarters where but narrow working space is available.

1 Other objects and features of the invention will lappear more fully indetail from the following driving -tool in condition to receive themandrel;

,-Fig; 2 is a similar yview kof the tool with the mandrel in placeandfully inserted into a dimpling die bymeansof said tool;A

Fig. 3 is an end ,elevation of the tool of Figs..

1 and2 as seen fromthe left or chuck end;

Fig. 4 is a side elevation of the shank a threaded portion,... integrali therewith and an associated plungenthe view`- showing the parts turneddegrees about the longitudinal axis of the shank from the position ofsaid parts in Figs. 1 to 3;

Fig 5 is anend elevation of the same parts shownV in liig. 4 as seenfrom the left end in the latter view; and

Fig. 6` is aside elevation of. the mandrel alone ofFigs. 1 and 2 whenturned or rotated 90 degrees aboutits` longitudinal axis from theposition of said views.

When kthe mandrel is yto be inserted into a rivet hole in oneor moremetal sheets to be dimpled, it is vusuallyiirst screwed into a holderand then passedthrough a dimpling die, etc., as disclosed in thePatentNo. 2,333,418, granted to the present applicant November 2, 1943, andthereafter individually into each of a plurality of such holes in thesheets and each time engaged by a power operated dimpling tool providedwith a second dimpling die to eiect dimpling about each hole. Duringsuch operation the mandrel remains in the vholder whichk is used toshift said mandrel from4 one hole to the next, being a convenient meansfor handling the mandrel and facilitating dimpling they sheets at higheciency.

However, frequently certain narrow spaces are encountered in or betweenthe metal sheets in which no adequate room is found for placing thementioned holder, and in which not even the full length of the mandrelalone can be accommodated, sothat the latter must obviously be insertedinto the rivet holes from the working side, that is', from the same sideupon which the dimpling to'oloperates. As the dimpling tool forms nopart of this'inve'ntion, it is superfluous to describe for the abovementioned patent discloses it in detail,

butin any case, the mandrel has a series of serraby said dimpling tooland a thread upon the other end.

With the foregoing objects in View and in order to make it feasible todimple metal sheets rapidly, even in narrow portions of structuresincluding them, it is proposed to insert the mandrel through the metalsheets from the dimpling side directly into a dimpling'dieibyf-sorewing"itiintlo: the latter when it'is'locatedon'the otherside ofsaid sheets,

while using a holder or handle to shift said die from one rivet hole tothe next and render the entire operation speedy and practical,as-willnzoiw be specically set forth.

Referring again to the drawings,=amarnirel` inserting tool, generallyindieatedfat-f rihas -a shank l l adapted for insertion into the chuckf2' of a hand drill or preferably ofgafgfiankeettype screw driver bywhich to rotate the tool under control and at will. The shank Ilisfintegral with the threaded portion or member I3 which is of greaterdiameterthan that Vof the'shankand which -,has an 'internal IboreMii-nto ,which al'hol low shank portion l5 ofamandreldriying plunger I6:extends .An interior Veimansion spring l1 occupies fthebore Miin memberIsand also Va bore lil insaid plungerandactivelytends .to urge said:plunger out of-said 'jeoire M. "The driving plunger IS has acylindrical head IB with opposite i depending portions lor along-ations2l iFig. E5, on two si-desextendingiinto-fthe open slots v'Z2 in thethreadedA m-ernber'llbwhich virtually forms a chuck coreforbase, fin/ordertozprevent relative rotationlof the -fplungerwith respect` to therest of the tool and especiallyitofthesshank tLwhile allowing free axialmovementfof said plunger into and out of member 'I3 fthe action ofspring I'I. Y

The front end 42:?,I of thenplungerheadis of coni-r cal formy anddiametrically acrossthesam-elis -cut awedge shaped slot -llladapted toreceivefone end of the mandreL-to'be described,-`said-endeengagingagainst agronp ofchuckv jaw-s 2f5iwhosegrear ends 26 arecorrespondingly'inclined toftlagainst'the conical end 23 ofsaid head.'Ihevjawsare-,retained in mutual associationby means cfa chuck casing321, internally threaded at 28 andscrcwed in upon the th1eads'29ofm'ember Hi' againstgthe ring 3.o seated against the rear ,flange 3|onsai'd core A:member i3, the @casing 4Zljhaving a pair .of Qphositelflat portions V32 .adapting the `casing 'for engagement by ,a wrench toscrew the same von said member 13. flThe chuck.'casin g at the 'forwardend hasra forwardly tapered internal yyi/)all 33 engaging against,inclined portionsrl 'Upon the exterior forward endsof `the ,chuckpjawsin order to bring thelattertogetherbymeans of the drivingplunger Vit.under theforward .bias ordmF pulse4 of .the jawclosingspring ,IJ whenthedatter isallowed toact freelyupon fsaid ljaws through said -plunger.l

vIn order y,to fopen .thechuok .jaws endallow .i11- sertion into thechuckof a .drawpinorimandreL generally indicated -at3,5, a.;manuallyAsl'iiftable sleeved@ is slidably mounted externally -on the chuckcasing -and rearwardly provided .with -an inwardly turnedange 3J'servingas a-forward stop against the -rearend of the chuck casingtitlrto imitforward moyementfof `said sleeve. AThe latterhas an internalthread `33 iwith-n theiforwardiend into which the-chuck ca p. 39.isscrewed, while being preferably 4rknurled l,upon the exterior thereof toz improve the grip ,thereon v:(-not `shown) and-providedwith-apairof-.sidegapsfor openings 4l Lto-allow access tofthejlat sidesif32 of,thefchuck Y casing ifor Igripping :the-latter ,fby :a Wrench whenassembling or disassembling the tool. The cap 39, while having asubstantially flat outer face 42 is provided with a rearwardly directedfrustoconical portion 43 occupying the center area of the interior ofsaid cap around a central aperture 44 in the latter and abutting theouter ends [l5 of the chuck jaws which are inclined toward,thetdhuckrcasingto correspon'dto the inclination 'of -saidfrustocni-cal portion.

Obviously, if the sleeve 36 is seized by the hand hof the operator asindicated at 46 in Fig. 1 and `drawn:rearwardly while the tool is heldagainst rearward movement (the shank l l being clamped ytl'n'ersfeevewillrbec'aused to occupy the retracted 4position'shown-in said Fig. l incontrast with the Y normal ,positionindicated at 4l in broken lines,andthe interior central portion 43 will force the jaws 125 "rearwardly,and thereby the driving plunger i6 rearwardly against spring il. Due tothe simultaiieous release -of .the .jaws from intimatefcontactawith fthe:converging internal wall 33of the Achuck-casing `consequent upon theAseparating'or :wedgingraction of the conical portion 4B :against 'stheyinclined forward ends 45 of the. jaws 1in fcooperati-on Kwith thesimultaneousV separating -orwredgingfaction ,of the conicalfaceor ende213.' ofi-'the plunger Aagainst thecorrespondingly inclined rearrends=2l'of'these jaws, the latter will be-separatedtoa maximumlimitpositionwherein they-fengageagainstthe interior cylindrical wall: 4810ithe-casi-ng,1which provides adequate spacing apart of the 'jaws forrelease or ,insertion of a mandrel.

'The-mentionedmandrel is'provided at one end with'aregularlyspaced'series of circumferential serrations "HB (Fig. `6) adapting saidend to be effectivelygrippedV and pulled stronglyby alpower operatedfd'imp'ling tool,-the-extreme end having two inclined Lside :portions 5Iconverging :suiciently to vform-a wedge shaped end adapted to t into thetransverseslot '241m the -end of the plunger head so that rotation ofthe tool as a whole 'byimeans vof 'the screw driver or hand drillconnected to'theshankll will also cause'positive rotation of vthemandrel. vThe other endiof the mandrel is provided with a threadBZfadapting-the lattertobe'screwed into ya-di'mpling'die 53 having aconcave Jportioniil'into which the metal will be projected duringdimpling while the sides of said die have opposite at portions or slotsy55 cut ltherein to adaptthe die for engagement by a bifurcated holderorhandle 56 having an open slot51 upon ".the'end of `its longer limb'while the shorter limb 59 on'said handle has Va similar slot 6L IThehandle may thus be tted to the diefatteither end., the die fitting intothe slot in the end concerned so that v.it may be shifted from hole 'tohole as thedimpling proceeds and the mandrel is released therefrom. The.chuck jaws are `provided .with .rows of teeth 1 6'2 corresponding 4to.the serrations 49 upon theemandrel. When.,the latter is inserted byfirst forward vwhich rthereby also .forces rthe vjaws f or-4 Ward andtogether ,upon the serrations of the mandrel, with the result that thelatter is firmly...

gripped ,in the tool ready for positive -rotation therewith `uponrotation .of the tool .itself by attached. 4 Y

means .of thefscreew 'driveror Adrill to which itis,

A Ii then the metal about'the-rivet hole '631m a sheet metal-structure64 is to be dimpled, thelatterfhaving'garather restrictedv or narrowspace 65,',5'thf-die'li53 may be introduced into said spacearidfsupported by holder 56 with a threaded hole 66in said dieyregistering with the hole 63 in the sheet metal, -when the mandrelinserting tool above-described and with the mandrel projecting therefrommay begplacedy opposite the rivet hole with thev threaded end 52 of saidmandrel initially inserted into said hole. When the screw driver orhand' drilly is operated`l to rotate the chuck and consequently themandrel, the threaded end 52 of said mandrel will engage in the hole 66in said die and be quickly screwed into the latter until the slotted end61 of the mandrel projects beyond the die. If at this stage the outersleeve 36 is manually withdrawn again as indicated in Fig. l, openingthe chuck, the tool may be withdrawn While the mandrel remains in placein the rivet hole with the die supported thereby on the other side ofthe sheet metal within space 65. If a power operated dimpling tool (notshown) having a concave or frusto-conical dimpling die complementary tothe die 53 is then thrust in upon the mandrel and caused to engage thesame and the dimpling tool operated to dimple the sheets, the lattertool may then be released and the tool embodying the present inventionagain engaged upon the mandrel for removal thereof from the dimpledrivet hole and the die within. In order to effect this result, the screwdriver or hand drill etc., is of course operated to rotate in theopposite direction from that first used to insert the mandrel into thedie, and with the mandrel thus released from the die but yet held insaid tool, the die is shifted within space 65 to the next hole and themandrel again caused to engage in the die by means of the presentmanually rotated tool which is then again released for the dimplingoperation by the power -operated tool.

Upon occasional breakage of the mandrel, which is likely to occursomewhere along the threaded end 52 thereof, the slotted end 61 isreadily engaged by a common screw driver and the broken part removed byunscrewing the same from the die which is obiviously then immediatelyready for receiving a new mandrel.

As it is well known among those skilled in the art that a mechanicalscrew driver of the Yankee type can instantly be adjusted for righthandrotation when the handle thereof is depressed toward the work and aseasily adjusted for rotation in the opposite direction under the sameconditions, the adjustment for the right hand rotation will obviously beused during the screwing of the mandrel into the dimpling die beforeeach dimpling cycle and the adjustment for the opposite direction whenunscrewing said mandrel therefrom after each dimpling operation iscompleted.

While the mandrel inserting tool has thus far been described as a deviceor attachment to be inserted into the chuck of a hand drill or amechanical screw driver to replace the screw driver bit of the latter,it is self-evident that the tool can readily be combined with, and bebuilt in as part of, the mechanism of said mechanical screw driver, ifso desired. It is equally evident that the tool may be made wholly or lnpart of steel, bronze or of any other materials as conditions maysuggest.

In a divisional application, led March 15, 1945, Serial No. 582,955,there are claims to a mandrel inserting tool for screwing and unscrewinga 6. threaded mandrel into a correspondingly threaded dimpling die asillustrated and described in this parent application.

What is claimed is:

1. In combination, a mandrel having a shank, a threaded. end portion,and a serrated end portion including a series of annular anges, theoutside diameter of the shank, of the crests of the threads, and of theannular flanges being substantially equal so that the mandrel may bepassed through an aperture of substantially suchv diameter in a worksheet, and a die having a threaded bore to receive the threaded endvoithe mandrel, said die being slotted for the reception of a handle tohold the die in position for the threading of the mandrel therelnto.

2. In combination, a mandrel having a shank and a threaded end portion,the outside diameter of the crests of whose threads is no greater thanthe outside diameter of the shank, a die having a slot and a threadedbore, the bore being adapted to threadably receive the threaded endportion of the mandrel, and a holder insertable into the die slot tohold the die on one side of a sheet for threadably receiving the mandrelupon insertion of the latter from the other side of the sheet through aperforation in such sheet.

3. A combination, according to claim 2, in which the holder has anextension handle adapted to move the die through a space substantiallyequal to that dimension of the die which is in the direction in whichthe mandrel is inserted and to hold said die in position for threadablyreceiving the mandrel upon the insertion of the latter through aperforation in a work sheet.

4. A combination, according to claim 3, in which the mandrel is formedwith a portion including a series of annular flanges adapted to begripped by a pulling tool.

5. In dimpling lapparatus for sheet metal, a mandrel for holding athreaded dimpling die in operative position against a work sheet, saidmandrel comprising a shank portion, a threaded end portion having a kerfat the extremity thereof, a serrated end portion including a series ofannular ilanges, and a tapered extension to the serrated end portionadapted to transmit to the mandrel rotary motion imparted by a slottedtool for the screwing of the threaded end portion of the mandrel intothe threaded dimpling die, said threaded portion, shank portion andserrated portion all having equal diameters, said serrated portion beingadapted to cooperate with a correspondingly serrated tool to pull thedie member into position for dimpling after the mandrel has lbeenthreadably connected thereto.

6. In dimpling apparatus for sheet metal, a threaded dimpling die; and amandrel for holding said die in operative position against a work sheet,said mandrel comprising a shank portion, a threaded end portion having akerf at the extremity thereof, a serrated end portion including a seriesof annular flanges, and a tapered extension to the serrated end portionadapted to transmit to the mandrel rotary motion imparted by a slottedtool for the screwing of the threaded end portion of the mandrel intothe threaded dimpling die, said threaded portion, shank portion andserrated portion all having equal diameters, said serrated portion beingadapted to c0- operate with a correspondingly serrated tool to pull thedie member into position for dimpling after the mandrel has beenthreadably connected thereto; said dimplingdie having means associatedtherewith for the positioning of said die for :amamos FJEEESE Feb. 19,'19.01

-Name Date tLcxzen `Aug. 15, :1941 .Caminez QSeptO, Fischer .;Nov.2,:1943; Nordgren :Dem .-21, 184:3 Hurst Mar-.4.28, 1944, Tuttle ,-Dec.26, -Amtsberg :July `l5, .1194? FOREGN PATENTS Country Date GreatBrtainJune-26, .1941

